The telecommunication numbering plan in the US divides the country into area codes and includes within each area code a plurality of central office exchanges. The exchanges cover geographical subareas of the area codes, and each exchange serves a number of subscribers. The maximum number of subscribers that an exchange can serve is limited by the number of digits that define a subscriber within an exchange which, in the US is 10,000. When the subareas covered by exchanges are built up to approach 10,000 subscribers, additional exchanges must be added, and they are typically added without regard to whether the geographical subarea of one exchange overlaps in whole or in part the geographical subarea of another exchange. What is diligently maintained, however, is that an exchange should not straddle more than one area code. This restriction is imposed so that telephone companies can include identically identified exchanges in adjacent area codes without creating ambiguities. Actually, the ambiguity is avoided by requiring customers to dial an area code prior to dialing the exchange when customers wish to reach parties outside their area codes. Since, at least traditionally, customers called within their area code much more than outside their area code ("long distance"), avoiding the requirement to specify the area code was an appreciated feature.
The burgeoning number of cellular telephones and the increase in the number of homes with a multiple number of telephone lines (for fax service, telecommuting, etc.) is causing the local telephone companies to reduce the geographical size of area codes and to increase their number. Consequently, people are increasingly forced to include the area code in their dialing digit sequence even when dialing a number that is geographically very close. While this is not a new problem; it is being exacerbated with the increase in the number of area codes.
An arrangement that eliminates, or reduces, the number of times that subscribers need to include the area code when dialing would be very beneficial.